Before
humans walked on the moon...
We
crashed landed some probes onto the moon (starting with the
U.S.S.R.'s Luna 3 in 1959, and we also bounced a laser beam off of
the moon!
On
this date in 1962, MIT scientists bounced laser light—a series of
high-intensity red flashes—off of the surface of the moon, and then
detected the reflections back here on Earth. It was the first time
that a laser beam had crossed space.
Nowadays
we can can aim our lasers at the retroreflectors Apollo astronauts
positioned on the moon. This is an amazing feat, because the
reflectors are so small compared to the distance crossed, and of
course the moon is always in motion, orbiting around the Earth; the
accuracy of hitting the reflectors is like using a rifle to hit a
moving dime two miles away! By measuring the time it takes the
reflected light to return to Earth, we can measure the distance from
the Earth to the moon.
And
we can measure this very large distance incredibly accurately! It's
like measuring the distance between Los Angeles and New York to one
hundredth of an inch.
We
have discovered that the moon is spiraling away from the Earth at a
rate of 38 millimeters per year. Granted, this isn't an incredibly
fast retreat—but some scientists say that it is faster than
expected.
The
very precise, multiple measurements of the moon's distance have been
used as evidence that Einstein's general theory of relativity is
correct, as the theory predicts the lunar orbit discovered through
these measurements. Also, the presence of the reflectors has been
used as evidence that humans actually went to the moon. You wouldn't
think anybody would need to build a case that people went to the
moon—everybody knows about the Apollo program and the moon rocks
and the “one giant leap for mankind,” right?—but some people
have claimed that the moon landings were faked! There was even a
television show—supposedly non-fiction—that claimed to prove that
American astronauts never went to the moon. (Let that be proof that
you really, really, really can't believe everything you see on TV—not
even the news or “documentaries.”) Check out this website that
debunks the bad science in the moon-landing conspiracy theories.
Also
on this date:
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